10. STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Jun. 30, 2020

STOCK-BASED COMPENSATION

Summary of stock option activities

			Weighted
		Number of Shares	Average	Weighted
	Shares	Underlying	Remaining	Average
	Available for	Options	Contractual	Exercise		Intrinsic
	Grant	Outstanding	Life (Years)	Price		Value
Balance at March 31, 2020	2,522,314	8,135,791		$	6.17
Granted	(114,110)	114,110		$	7.65
Exercised	—	(321,188)		$	6.21	$	428,272
Forfeited	9,250	(9,500)		$	7.92
Balance at June 30, 2020	2,417,454	7,919,213	5.48	$	6.19
Options vested and exercisable		5,407,382	4.18	$	5.64	$	8,712,915
Options vested and expected to vest		7,859,438	5.46	$	6.18	$	9,282,831

Schedule of options outstanding by exercise price

				Number of	Options Outstanding			Options Exercisable
				Shares	Weighted		Weighted Average		Weighted
				Underlying	Average		Remaining	Number	Average
				Options	Exercise		Contractual	Vested and	Exercise
Exercise Price				Outstanding	Price		Life (Years)	Exercisable	Price
$	3.40	-	4.81	902,585	$	4.06	3.82	902,585	$	4.06
$	4.90	-	4.99	1,316,046	$	4.97	4.95	1,316,046	$	4.97
$	5.13	-	5.59	926,721	$	5.32	4.14	891,496	$	5.32
$	5.69	-	6.28	838,702	$	5.99	4.55	650,263	$	5.98
$	6.45	-	6.70	1,197,400	$	6.63	5.41	652,453	$	6.58
$	6.82	-	7.26	1,192,855	$	7.06	5.47	661,556	$	6.95
$	7.40	-	8.06	737,571	$	7.75	8.82	135,626	$	7.59
$	8.09			83,860	$	8.09	7.58	41,804	$	8.09
$	8.30			614,893	$	8.30	9.07	46,973	$	8.30
$	9.20			108,580	$	9.20	0.59	108,580	$	9.20
				7,919,213	$	6.19	5.48	5,407,382	$	5.64

Summary of stock-based compensation expense by line item

	Three Months Ended June 30,
	2020		2019
Cost of revenues	$	88	$	55
Research and development		413		399
Selling, general and administrative		254		197
Total	$	755	$	651

Schedule of weighted average assumptions

	Three Months Ended June 30,
	2020		2019
Stock Option Plans:
Risk-free interest rate	0.36	%	2.30	%
Expected life (in years)	5.00		5.00
Volatility	41.9	%	37.3	%
Dividend yield	—	%	—	%
Employee Stock Purchase Plan:
Risk-free interest rate	0.15	%	2.43	%
Expected life (in years)	0.50		0.50
Volatility	67.1	%	43.1	%
Dividend yield	—	%	—	%